This article compares two missionary grammars written in the middle of the 17th century, Horacio Carochi’s (1579–1662) Arte de la Lengua Mexicana con la declaración de los adverbios della (1645) and John Eliot’s (1604–1690) The Indian Grammar Begun: or, an Essay to Bring the Indian Language into Rules (1666). Although published only 21 years apart, the two works differ in both context and theoretical underpinnings. These differences are manifested both in the type and depth of analysis undertaken by each author. Indeed, Carochi’s analysis goes much deeper and offers a more complete description of the language treated. While this can be attributed in part to Carochi’s own linguistic ability, the quality and completeness of his grammar is due in large part to the existence of a tradition of scholarship concerning Nahuatl in New Spain, a tradition that is strikingly absent in New England of the time.